Dependence of mechanical properties on crystallographic orientation in nickel-based superalloy Hastelloy X fabricated by laser powder bed fusion

In the present study, solid solution strengthened Ni-based superalloy Hastelloy X (HX) parts were fabricated using the laser powder bed fusion (LPBF) additive manufacturing process with the intent of developing a strong crystallographic texture. Their tensile properties at room temperature were investigated along the < 100 > , < 110 > , and < 111 > crystallographic orientations. Tensile behavior was found to be highly dependent on the crystallographic orientation and present unique combinations of strength and ductility when compared with other LPBF-HX counterparts. EBSD (Electron backscatter diffraction) analysis after fracture revealed deformation twinning in the < 110 > and < 111 > samples, but not in the < 100 > orientation. It was observed that crystallographic orientation had a great impact on the effective stacking fault energies. Critical stress for deformation twinning was also observed to be crystallographic orientation-dependent. It was close, if not below the yield strength (YS) for < 110 > and < 111 >, while it was well above the ultimate tensile strength (UTS) of the < 100 > orientation. The YS value of < 111 > (807 +/- 28 MPa) was higher than that of < 100 > (693 +/- 8 MPa) and < 110 > (648 +/- 13 MPa). The results suggest that deformation twinning can occur in solid solution strengthened Ni-base superalloys at room temperature, and their formation does not mandatorily require the presence of gamma' precipitates or thermally assisted mechanisms. In contrast to the < 100 > and < 111 > orientations, rotation of the lattice after deformation was found for the < 110 > . (C) 2021 Published by Elsevier B.V.

Automated summary

Solid solution strengthened Ni-based superalloy Hastelloy X parts were fabricated using the laser powder bed fusion (LPBF) additive manufacturing process to develop a strong crystallographic texture. Tensile properties at room temperature were highly dependent on crystallographic orientation, with unique combinations of strength and ductility observed. Deformation twinning was found in the <110> and <111> samples, but not in the <100> orientation, with significant impact of crystallographic orientation on effective stacking fault energies and critical stress for deformation twinning.